1. Field of the Invention
The present invention relates to an apparatus for variable flow control for precision applications, such as agrochemical applications. The invention is directed towards a flow control device comprising a metering rod moveably mounted within a housing. The position of the metering rod is controllable so as to control the flow rate, flow angle and/or droplet size of fluid passing through the flow control device of the present invention.
2. Description of the Prior Art
The ability to vary the application rate of agrochemicals is highly desirable in the field of precision farming. Variable rate applications of chemicals are desirable to respond to changes in soil and/or crop and/or pest conditions.
There are at least three prior art methods for variable rate agrochemical applications. The first method varies the nozzle pressure to alter the spray rate. This method is unsatisfactory because pressure must be increased by a factor of four in order to double the spray rate. Pressure increases of this magnitude decrease the droplet size and result in difficulties maintaining a selected spray pattern at low pressures.
A second prior art method of variable rate application is to equip an applicator with several application systems having different capacities. Such systems can be turned on or off in response to changes in crop and/or soil and/or pest conditions. This method is unsatisfactory because it is electromechanically complex and it provides only stepwise variations, rather than continuous variations, in flow rate. Stepwise variations limit the suitability of such devices for crop and/or soil and/or pest conditions that require only slight variations in application flow rates.
A third prior art method for achieving variable rats agrochemical application is the use variable rate flow control nozzles on a spray system, such as a boom sprayer. Prior art devices employing this method have incorporated pulsed solenoids into a nozzle body to control application rate and drop size. In a typical boom spray system, nozzles are spaced out approximately every 20 inches. In such a system, a pulsed solenoid flow control apparatus is electrically complex and subject to harsh boom conditions, and more importantly is limited in range of flow rate since the solenoid is only in series with a nozzle orifice.
The present invention provides a true variable rate flow control device which is robust and which is capable of controlling flow rate, droplet size, and/or spray angle through the use of a control pressure or other rod driving means.